It is revealed in a Court of Mist and Fury that Keir, Morrigan's father, in an attempt to woo the Autumn Court into an alliance, offered his daughter Morrigan's hand in marriage to Beron's eldest son, Eris. Due to Eris' reputation for cruelty, Morrigan decided to lose her virginity to Cassian, a bastard-born Illyrian, so that she would not have to marry Eris. When Eris hears of this, he refuses to marry her, claiming that she had been 'sullied by a bastard-born lesser faerie', thus ruining Keir and Beron's fragile alliance. In response, Morrigan's family left her on the Autumn Court border with a note nailed to her body that announced that she was Eris' problem. Eris, however, ignored her and left her in the middle of the woods to die. 
In A Court of Wings and Ruin, Eris and his brothers happen upon Lucien and Feyre, who had just fled from the Spring Court and were traveling to the Night Court on foot until they regained their magic. Feyre and Lucien manage to escape their clutches, and Eris and his brothers subsequently attempt to hunt them down. However, Feyre and Lucien manage to make it to the Winter Court borders and are then rescued by Azriel and Cassian. Eris and his brothers are overwhelmed and bested by the Illyrian warriors, but Feyre, however, decides to spare them. The Autumn Court sons flee back to their homeland relatively unscathed.
Later on, Eris allies himself with the Night Court, however slightly. Hungry for power and his father's throne, he strikes a deal with Rhysand. In exchange for his help in seducing Keir into an alliance with Rhysand against Hybern, Eris was guaranteed Rhysand's support should he decide to overthrow his father and claim his father's throne. During the course of the novel, Beron's support of the resistance toward Hybern fluctuates, and it is considered by the Night Court to kill Beron and crown Eris, earning a more steadfast ally. Ultimately, Beron does decide to support Rhysand and aides the Night Court and their allies in the final battle against Hybern in the Mortal Lands, albeit after being threatened and practically forced by Tamlin.
Eris also claims to have refused to participate in the torture and death of Jesminda, Lucien's lesser Fae lover, and also that it was he who saved Lucien's life later by alerting Tamlin to his presence near the Spring Court border. Tamlin then saved Lucien from his brothers and Lucien defected to the Spring Court. He also claims to have ended his engagement with Morrigan because he knew she did not desire the union, not because of his disgust at her union with Cassian. All of this, however, is unsubstantiated claim.
- A Court of Thorns and Roses (First appearance)
- A Court of Mist and Fury (Mentioned only)
- A Court of Wings and Ruin
- ↑ A Court of Mist and Fury: Chapter 41
|Amarantha · Amren · Azriel · Cassian · Elain Archeron · Feyre Archeron · King of Hybern · Lucien · Morrigan · Nesta Archeron · Rhysand · Tamlin|
|Minor and supporting characters|
|Alis · Andras · Beron · Bron · Cerridwen · Clare Beddor · Cresseida · Devlon · Eris · Graysen · Feyre's father · Hart · Helion · Ianthe · Isaac Hale · Isaac Hale's wife · Jurian · Kallias · Keir · Mercenary · Miryam · Mortal Queens · Mrs. Laurent · Naga · Nuala · Unnamed Summer Court Faerie · Tarquin · The Bogge · The Bone Carver · The Suriel · Thesan · Tomas Mandray · Varian · Weaver|
|Aunt Ripleigh · Dark Mother · Drakon · Feyre's mother · Ianthe's father · Ianthe's mother · Ianthe's sisters · Miryam's father · Miryam's mother · Mother · Rhysand's father · Rhysand's mother · Rhysand's sister · Nostrus · Queen of the Black Land · Tamlin's mother · Tamlin's father|